1. Field of the Invention
The present invention relates to an antenna device and a radio communication device.
2. Related Art
A size of an antenna depends on operating frequency. For example, with high-frequency wavebands such as the millimeter waveband, the short wavelength of the operating frequency enables downsizing of an antenna and incorporation thereof into a semiconductor package. In order to mount an antenna into a semiconductor package, the antenna must be mounted in proximity to a semiconductor chip. As an example of mounting an antenna onto a substrate, a radio frequency tag device is known in which wires operating as an antenna are bonded to a semiconductor chip (for example, refer to FIG. 4 of JP-A 8-88581 (Kokai)).
This radio frequency tag device includes a semiconductor chip fixed on a substrate and one or more wires that operate as an antenna, and is covered by an organic covering. The wires have both ends connected to the semiconductor chip by wire bonding, and operate as an antenna. The lengths of the wires are determined by the frequency of a radio frequency signal.
According to the conventional radio frequency tag device described above, since the wires that operate as an antenna are directly connected to a semiconductor chip, a short feeder between the antenna and a circuit element will suffice, resulting in an advantage in that feeding loss can be reduced. However, with the conventional radio frequency tag device, since the vicinity of a feeding point where current intensity is high and which is a main radiating source is in proximity to the semiconductor chip, there is a problem in that electromagnetic waves are absorbed by the semiconductor chip, causing significant deterioration in efficiency and gain.
In addition, this radio frequency tag device assumes frequencies up to the microwave band. In the case where the wavelength is somewhat long such as in conventional radio communication using the microwave band, production errors including a certain degree of misalignment in wire bonding positions can be ignored. However, in the case of high frequencies (millimeter waveband or higher) where the wavelength is short, there is a problem in that production errors such as misalignments in wire bonding positions become too large to ignore, thereby affecting antenna characteristics.